SALICIN, the bitter principle of willow bark, was discovered by Leroux in 1831. It exists in most species of Salix and Populus, and has been obtained to the extent of 3 or 4 per cent. from the bark of S. helix and »S'. pentandra. According to Herberger, the bark of the young branches affords salicin in larger proportion than that of the trunk and contains less of the other ingredients which interfere with its extraction. Salicin is prepared from a decoction of the bark by first precipitating the tannin by milk of lime, then evaporating the filtrate to a soft extract, and dissolving out the salicin by alcohol. As met with in commerce it is usually in the form of glossy white scales or needles. It is neutral to test paper, inodorous, unaltered by exposure to the air, and has a persistently bitter taste. It is soluble in about 30 parts of alcohol or water at the ordinary temperature, and in 07 of boiling water or in 2 parts of boiling alcohol, and more freely in alkaline liquids. It is also soluble in acetic acid without alteration, but is insoluble in chloroform and benzol. From phloridzin it is distinguished by its ammoniacal solution not becoming coloured when exposed to the air. Cold sulphuric acid dissolves salicin, forming a bright red solution. When salicin is heated with sulphuric acid and potassium bichromate, salicylic aldehyde (C 7 H 6 O 2 ) is formed, which possesses the odour of meadowsweet flowers (Spiraea Ulmaria, L.).

Salicin is chiefly used in medicine as an antipyretic in acute rheumatism, for which it is given in doses of 5 to 30 grains. Its action is less powerful than that of Salicylic Acid (q.v. ), and its depressing effect on the circulation is less marked. It is also given for headache and for ague....